As the heir of an wealthy Athenian sculptor, Socrates used his financial independence as an opportunity to invent the practice of philosophical dialogue. Since he wrote nothing of his own, we are dependent upon contemporary writers like Aristophanes and Xenophon for our information about his life. After dignified service as a soldier in the Peloponnesian War, he lived for the rest of his life in Athens and devoted nearly all of his time to free-wheeling discussion with its aristocratic young citizens, insistently questioning their confidence in the truth of popular opinions, even though he often offered no clear alternative. Unlike the professional Sophists, Socrates declined to accept payment for his work with students, many of whom were fanatically loyal to him. Their parents, however, were often displeased with his influence, and his association with opponents of the democratic regime made him a controversial political figure. An Athenian jury officially convicted Socrates (of corrupting youth and interfering with the religion of the city) and sentenced him to death in 399 B.C.E. Accepting this outcome, Socrates drank hemlock and died in the company of his friends and disciples.

Our best sources of information about Socrates's philosophical views are the early dialogues of his student Plato, who attempted to provide a faithful picture of the methods and teachings of the master. Here the extended conversations of Socrates aim at understanding (and, therefore, achieving) virtue {Gk. areth [aretę]} through the careful application of a dialectical method that uses critical inquiry to undermine the plausibility of widely-held doctrines. In Euqufrwn (Euthyphro), for example, Socrates systematically refutes the superficial notion of piety or moral rectitude defended by a confident young man. Plato's Apologhma (Apology) is an account of Socrates's (unsuccessful) speech in his own defense before the Athenian jury; it includes a detailed description of the motives and goals of philosophical activity as he practiced it. The Kritwn (Crito) reports that during Socrates's imprisonment he responded to friendly efforts to secure his escape by seriously debating whether or not an individual citizen can ever be justified in refusing to obey the laws of the state.

The Socrates of the Menwn (Meno) investigates the nature of virtue, defending the doctrine of recollection as an explanation of our most significant knowledge and maintaining that knowledge and virtue are so closely related that no human agent ever knowingly chooses evil: improper conduct is a product of ignorance rather than of weakness of the will {Gk. akrasia [akrásia]}. The same view is also defended in the PrwtagoraV (Protagoras), along with the unity of the virtues. Although Socrates continues to appear as a character in the later dialogues of Plato, these writings more often express philosophical positions Plato himself developed long after Socrates's death